Increases the XP gain rate for the Logic skill. Remember that a high Logic skill also increases the speed of learning other skills, so a Sim with Genius indirectly can learn all skills faster than normal. Pairing Genius with Bookworm and spending all your time in the library will let you gain skills through books alone in record time.

The Genius trait also increases the chance a Sim will win a game of chess, and increases his take from a successful hack at a computer (if the Sim is also has the Computer Whiz trait).

Applies a buff when this Sim does any good-natured action, especially social interactions. The Sim also gains a few special social interactions, including one that can cancel another Sim's debuffs (in the form of comforting them). Sims with the Good-trait are the ultimate team players, best used for families.

Greatly increases the chance the Sim's joke social interactions pass (unless the target has the No Sense of Humor trait). There is no direct correlation with an increase of the relationship gain, but with Good Sense of Humor, your Sim can tell jokes and gain it pretty fast that way. Especially paired with Charismatic and/or Friendly, you can make friends pretty quickly.

Greatly increases the chance of any kiss-type social interaction is accepted, even early in the relationship. When paired with Flirty or Hopeless Romantic, a Sim can get anyone in the mood for Woo Hoo pretty rapidly.

Increases the speed and quality of the Sim's gardens, and allows the Sim to revive dead plants. Sims without this trait can buy the Super Green Thumb Human lifetime reward to offset it if necessary, but Sims with the trait can garden well pretty much from the beginning.

This trait is compatible with all others, including Hates the Outdoors for some reason.

Increases the negative effect of all debuffs; buffs are unaffected. That means these Sims are often in a bad mood and have a tough time staying happy, indirectly hurting their job performance at conventional careers. This is a negative-only trait, to be used when you want a challenge.

Increases the XP gain rate of the Mechanical skill, decreases the chance objects break at all, and decreases the time it takes to upgrade or repair objects. Also makes the Sim unable to die by electrocution while standing in a puddle.

Applies a debuff whenever this Sim is outdoors. The debuff is moderate strength, so it's tough to ignore it. Definitely a challenge, this makes farming or firefighting incredibly difficult, though not impossible.

Allows the Sim to sleep through emergencies, for better or worse. Sims with the Heavy Sleeper trait also snore, which can bother their bed partner if he or she is a Light Sleeper. Despite the in-game description of this trait, the Sim will still wake up when the alarm clock rings.

Increases the chance that all romantic-type interactions are accepted, and the chance that this Sim will accept others' romantic-type interactions. Paired especially with Great Kisser, the Sim will be able to get any Sim ready for Woo Hoo in a short amount of time.

Hopeless Romantic Sims are not inclined either way to prefer many Sims or only a single Sim. If you pair Hopeless Romantic with Family-Oriented, this Sim will probably want to have many romantic moments with his or her spouse. If you pair Hopeless Romantic with Flirty, this Sim will try to bed the entire town.

Causes the Sim to get angry quickly when unhappy. That means when any debuff is present, this Sim is quicker to use aggressive negative social interactions. This one can be a lot of fun paired with Disciplined and Evil, allowing the Sim to basically just pick fights all day long for his own amusement.

Applies a buff when the Sim upsets another Sim, and tends not to dress in their formal attire even for formal parties. This Sim is a jerk, but enjoys being a jerk, so the trait is a net positive one even if relationships become a little tougher as a result.

This Sim exhibits unpredictable behavior, including wearing whatever outfit he wants to regardless of the situation. This Sim also gains the "Talk to Self" self-interaction, providing a Social meter boost even when no one else is around.